interjection similar in meaning to fooled you! or gotcha! after a prank. It first appeared in the tv sitcom The Big Bang Theory and is used by the character named Sheldon.
It probably comes from the word zing and ba and a may just have been added for added effect. See video of Bazinga!-moments

1. chatter, prattle 2. to make an abrupt striking sound or series of sounds, such as footsteps 3. cry of a bird , especially fowl. see also: cackle, cluck 4. Sound of a late 19th century gun being closed after loading, according to a reply to a yahoo!Answers post about the sound of old guns

the "sound" of someone stealing something. the word is spoken to make obvious or humorous the playful theft of an item in front of others. (e.g. "you shouldn't leave your wallet lying around like that...Yoink!". used often in the cartoon series "the Simpsons")